SRSG electrode spacing

I have got the 2% thorium rod (red welding electrodes), and a quote from
a tool grinding firm, for cutting and rounding the electrodes, this
leads to a couple of questions:

1) How much rounding of the electrodes is desirable?. 
Since anything from just deburring the edges to a full hemisphere is
possible, I would appreciate guidance for powerlevel 3 kW:(1/4 "
electrodes) and 10 kW (3/8 " electrodes) Both 3000 RPM (50Hz) 2 rotating
electrodes, Amount of stationary electrodes will depend upon breakrate,
but probably 4 sets for 200 bps, to keep cap size down to manageable

2) Which total spacing should i use ?.
I could space them as close as motor endfloat allowes, so that the gap
will be very short, this will make the gap fire before the electrodes
align, making the gap distance decrease during dwell, create a long
dwell period, and also present a short gap for the transformer to arch
into, after the primary ringdown. This may not matter, since the cap
will pull the voltage down. Hmmm.....

Setting the electrodes wide, like creating a breakdown voltage across
the fully aligned electrodes equal to the desired total breakdown
voltage would result in a very short dwell period, but the arclength
would also not get shorter during dwell.

I suppose something inbetween will be needed, so any experiences on this
subject will be appreciated.

Cheers, finn